Patients with intra-aortic balloon pumps (catheters placed in the groin connected to a pump which assists the heart by opening and closing a balloon in the aorta, thereby decreasing the work of the heart and improving blood flow to the coronary arteries) often receive intravenous (IV) heparin (a "blood thinner") to prevent circulation problems in the leg (where they are inserted). When intra-aortic balloon pumps were initially developed, the catheters were larger than the catheters used today. Due to the large size of the catheter and the material used to make the catheter, it was thought that intravenous heparin would prevent poor blood flow to the leg that contained the temporary catheter. Intravenous heparin, however, has never been proven to maintain good blood flow in these patients. The catheters used with intra-aortic balloon pumps are now smaller in size and made of a material that is less likely to produce blood clots. It is not clear that heparin is needed with intra-aortic balloon pumps. Bleeding complications associated with intra-aortic balloon pumps may be decreased if heparin is not used. In 2004, 99 patients received intra-aortic balloon pumps in the cardiac catheterization labs at William Beaumont Hospital. These patients received intravenous heparin and experienced a large number of bleeding complications (27 patients required a blood transfusion). This study will help the investigators to clarify if heparin should or should not be routinely used in patients with intra-aortic balloon pumps.